Human Body Cell Renewal

Study Notes

Body Renewal and Nutrient Absorption

The body constantly regenerates; about 5% of body weight is replaced daily through new tissue growth.
Taste cells regenerate every 7 days, intestinal cells every 1 to 3 days, skin cells monthly, and red blood cells every 120 days.
Nutrients in food serve as raw materials for bodily maintenance, obtained through digestion and absorption.

Digestive Tract Overview

The digestive tract functions as the body's food processor, stretching 25 to 30 feet from mouth to anus.
Organs like the pancreas and liver release digestive juices, with a significant part of digestion handled by enzyme systems from salivary glands, stomach, and pancreas.
Enzymes are complex proteins that facilitate chemical reactions without changing themselves, making them reusable.

Key Digestive Organs and Their Functions

Salivary Glands: Produce enzymes for starch and fat breakdown.
Tongue: Aids in chewing and mixing food with saliva.
Esophagus: Transports food to the stomach.
Stomach: Secretes protein and fat-digesting enzymes, mixing and liquefying food.
Liver: Produces bile, essential for fat digestion.
Gallbladder: Stores and secretes bile.
Pancreas: Secretes enzymes for carbohydrates, protein, and fat breakdown.
Small Intestine: The primary site for carbohydrate, protein, and fat digestion.
Large Intestine: Absorbs water and houses intestinal bacteria.
Rectum: Stores waste for excretion.
Anus: Controls release of waste.

Digestive Enzymes

Carbohydrate Digestion:
- Amylase: Produced in salivary glands and pancreas; breaks down starch into glucose chains.
- Sucrase: Produced in the small intestine; converts sucrose into glucose and fructose.
- Lactase: Breaks down lactose into glucose and galactose in the small intestine.
- Maltase: Also in the small intestine; separates maltose into glucose molecules.
Fat Digestion:
- Lipase: Found in salivary glands and pancreas; breaks fats into fatty acids and glycerol.
Protein Digestion:
- Pepsin: Predominantly in stomach; separates proteins into shorter amino acid chains.
- Trypsin: Produced in the pancreas; splits chains of amino acids.

Digestion and Absorption

Digestion concludes when carbohydrates, fats, and proteins are reduced to substrates like monosaccharides, fatty acids, and amino acids.
Nutrient absorption occurs primarily in the small intestine, with end products absorbed also in the stomach and large intestine.
End Products of Digestion:
- Carbohydrates → Monosaccharides and Disaccharides
- Fats → Fatty acids and glycerol
- Proteins → Amino acids

Digestive Process Insights

Hydrochloric acid in the stomach helps uncoil protein strands.
Undigested fiber is carried away by the large intestine.
Saliva prepares fats for lipase action.
Starch digestion begins in the mouth, with food typically remaining in the stomach for 2-3 hours, liquids passing through in about 20 minutes.
If laid flat, the surface area of the small intestine is comparable to a football field.

Description

Explore the fascinating process of cell renewal in the human body. This quiz delves into how often different types of cells are replaced and the significance of this continuous change. Test your knowledge about the dynamics of bodily tissues and how they contribute to overall health.